(The Computer Engineer) says: "Most manufactures of Copper heatsinks use a thin coating of laquer or other sealant to ensure that the copper doesn't react with the Oxygen and form the all to often seen 'green facia' or weathering. This would be fatal to thermal conductivity, so the coating is there to protect the copper from becoming copper oxide. However, it is possible that these 'laquers' are interacting chemically with the compounds used in the PCM from Nanotherm.